Loudspeakers under certain conditions are susceptible to a variety of forms of distortion. Loudspeaker distortion can be irritating to a listener. For example, “rub and buzz” distortion occurs when a loudspeaker cone hits a part of the loudspeaker. This occurs when the inward displacement of the loudspeaker cone is too great. This distortion in application such as cell phones can lead to not only poor quality reproduction, but can be so bad that the speech is unintelligible. With the movement towards smaller and cheaper loudspeakers in today's consumer electronics, the problem is only exacerbated.
At present, loudspeakers are at best measured for distortion in the factory and those that don't meet specifications are simply discarded.